Conventionally, for connection or disconnection of a communication line of a telephone, means have been employed such as a hook-type device for a fixed telephone set and switching of a call button for a portable telephone set. However, there have been issues such that the hook-type device restricts a design-property of a telephone set and that the call button type confounds the operation of a telephone set.
The recent spread of portable telephones sees the issues of the switch-type method such that a communication line is not disconnected owing to carelessness, and that a malfunction occurs in a call button or other buttons of a portable telephone in a pocket or in a bag without a user's intent. Particularly, the malfunction of a call button is problematic.
Correspondingly, a cordless telephone set is described in Japanese unexamined Utility Model Publication No. 04-94842 which is provided with a switch for switching according to the movement of an ear pad and a detection circuit for detecting the switching, so as to make connection to a communication line only by pressing an ear into a receiver to allow the operation to be simplified.
A personal wireless portable telephone communication device is described in Japanese unexamined Patent Publication No. 06-46123 which contains a range detection device for detecting the distance between a receiver and its user's ear having an infrared photodetector for detecting an infrared source and the reflected light thereof. This is the technology that when the distance between a receiver and its user's ear is detected as shorter than an arbitrary threshold value, the receiver operates in a hand-held receiver mode, and that when the distance is detected as longer than the arbitrary threshold value, the receiver operates in an open-type loudspeaker mode. This gazette describes that other distance measurement systems such as an acoustic echo system are applicable instead of infrared light.
However, the invention described in Japanese unexamined Utility Model Publication No. 04-94842 arranges a plurality of movable mechanism components such as an ear pad and a switch, and consequently, is disadvantageous in that a cordless telephone device becomes more complex with the mechanism components.
Furthermore, the invention described in Japanese unexamined Patent Publication No. 06-46123 is disadvantageous in the following points. The distance between a receiver and its user's ear is detected by measuring the illuminance or intensity of reflected light; however, light is reflected even when all substances including human tissue other than an ear, paper, metal, plastic, ceramics, and biological tissue approach a receiver. When the reflectivity of a relevant substance is lower than the reflectivity of an ear, a malfunction does not occur; however, when a substance having higher reflectivity than an ear (for example, glasses and earrings) exists adjacent to an ear and gradually approaches a receiver from a long distance, there is a possibility that the malfunction of the recognition that the substance is close by a receiver occurs at a distance position longer than a prescribed threshold value. This malfunction similarly occurs when a detection means, even which might even be sound, approaches a substance of some kind.
Thus, the method for finding a distance based on the illuminance or intensity of reflected light or reflected sound has to determine the distance based only on information of the external surface of a substance, and consequently, a malfunction tends to occur. In order to avoid this, it is preferable to employ a judgment criterion which considers the structure and materials inside a living body as well.
Taking the above factors into consideration, an objective of the present invention is to provide a call control device and a call control method therefor, which easily allow a telephone call to be controlled using an auditory organ, which every human has, without a complex mechanism component.